The present invention relates to a governor for aircraft propellers and more specifically to electronically controlled governors which provide their own power.
Governors for variable pitch propellers are well known and usually comprise a device mounted on and driven by the engine which senses and controls propeller (RPM) by hydraulically adjusting the pitch of the propeller. A common type of governor employs a hydraulic 3-position spool valve with a flyweight type actuator connected thereto to shift the valve spool in one direction or the other as the centrifugal force of the rotating flyweights increase or decrease spring force acting on the valve member which opposes the force of the flyweights. As the propeller begins to over speed, the increasing centrifugal force on the flyweights overcomes the speeder spring and shifts the valve spool so as to allow oil to flow to a hydraulic cylinder in the propeller hub which increases the pitch of the propeller blades thus increasing torque of the propeller causing the propeller speed to slow down to maintain the original RPM setting of the governor. Mechanical governors of this type for controlling variable pitch propellers have been available on airplanes for the better part of this century. They are typically used in a constant speed propeller governing system wherein the load on the engine varies and the propeller blade must change its pitch so as to maintain a constant RPM. Propeller governors have previously been electrically actuated, as taught in U.S. Pat. Nos. 3,831,615 and 3,751,993. However, both of these patents sense speed mechanically while the present invention senses speed electrically with the use of a small generator.
The general concept of a prime mover for a vehicle driving a generator goes back to the early automotive days. Locating the generator on a rotating propeller hub to provide electrical energy for changing pitch of the blades is taught in U.S. Pat. No. 4,556,366 and U.S. Pat. No. 2,491,172. These two patents also teach using the produced electrical energy for other functions.